Gastroesophageal reflux occurs when stomach acid intermittently surges into the esophagus. It is common for most people to experience this acid reflux occasionally as heartburn. Gastroesophageal reflux disease (GERD) is a clinical condition in which the reflux of stomach acid into the esophagus is frequent enough and severe enough to impact a patient's normal functioning or to cause damage to the esophagus. GERD is sometimes also referred to as “reflux” or “reflux esophagitis”.
In known methods for gastroesophageal reflux monitoring a pH sensing device is held in the lower esophagus and the pH levels therein are monitored for a period of time (usually 24–48 hours). The device may be attached to the esophageal wall or it may be suspended in the esophagus from an extension (e.g. catheter or cord). The known methods for in-vivo pH monitoring, specifically for gastroesophageal reflux monitoring, typically measure pH prevailing in a body lumen, such as the esophagus, however they usually do not measure other parameters of a pH reflux, such as pH gradient.